1. Technical Field
The present invention relates to a flame-retardant insulated electric wire obtained by coating an aluminum-based conductor with a flame-retardant resin composition.
2. Background Art
Hitherto, as flame-retardant insulated electric wires to be routed in automobiles, those obtained by coating a copper (Cu) wire with a resin composition using a polyvinyl chloride resin as a base resin have been frequently used. A polyvinyl chloride resin has excellent material properties such as flame retardancy and mechanical properties. However, there has arisen an environmental problem since harmful gases such as halogen-based gases are generated when the polyvinyl chloride resin is burned at incineration, vehicle fire, or the like.
Accordingly, in recent years, as halogen-free resin compositions, there have been developed resin compositions using a polyolefin-based resin and an olefin-based resin or a styrene-based resin as a base resin (for example, see JPA-2008-231317). In order to form a halogen-free insulating coating, the resin composition inevitably requires large amounts of additives owing to the properties of a copper wire. Namely, in the resin composition, long-term stability of mechanical strength is improved through prevention of decomposition and deterioration by adding various additives to the above base resin. As a specific example, it is necessary to include 50 to 100 parts by weight of a metal hydrate and, as additives, 3 to 5 parts by weight of a phenol-based antioxidant, 0.1 to 1.0 part by weight of a salicylic acid-based metal scavenger, 3 to 5 parts by weight of a hydrazine-based metal scavenger, and 1 to 10 parts by weight of a metal oxide into 100 parts by weight of a base material composed of a polyolefin-based resin and an olefin-based resin or a styrene-based resin. Thus, when amounts of the additives to be added increase, there is a problem that weight increases as a whole flame-retardant insulated electric wire.
In recent automobile parts, weight saving is desired and hence weight saving is required even as an electric wire for automobiles. Accordingly, it has been proposed to change a conductor from copper (Cu) into aluminum (Al).